In 2013, huge active plumes containing water vapour being released from the surface of Jupiter’s moon Europa were discovered. This sensational find was made using the NASA/ESA Hubble Space Telescope. Europa has been a focus of extraterrestrial research for some time now, as there were clear indications that it harbors a liquid ocean beneath its icy crust. Now, it appears, the geysers have vanished.

The existence of the plumes "is the kind of thing that could have a profound impact on how we explore Europa," Curt Niebur, outer planets program scientist at NASA headquarters, said during a NASA planetary sciences subcommittee meeting. "With an ocean that is tens of kilometers below the ice, most likely, if you can have a plume that's possibly bringing material from that ocean up to orbit, well, that's going to affect how you explore," Niebur added.

Lorenz Roth of the Southwest Research Institute in San Antonio, Texas and Joachim Saur of the University of Cologne used the Hubble to prove that there is water vapour erupting near its south pole. The water plumes are in comparison to earth geysers immensely large and reach heights of approximately 200 km. Europa has a circumference of 3200 kilometers, comparable in size with the Moon.

But new Hubble observations in January and February of this year showed no signs of the massive plumes. "It could be just the way that we use the auroral emissions coming from those plumes at the UV [ultraviolet] wavelengths of light that we use with Hubble," discovery team member Kurt Retherford, of the Southwest Research Institute in San Antonio, told Space.com. "These things depend on Jupiter's plasma environment," Retherford added. "Maybe there were just a lot of particles, atoms, getting excited by electrons and ions in Europa's atmosphere, more so than at other times, and [they] just lit up the plumes more than they usually do."

Retherford added that the plumes may sometimes simply be too small to see by the scientists who are relying on the Earth-orbiting Hubble to study the features on Europa, Retherford said. Another possibility Retherford noted is that the geysers don't exist, that the detection by Hubble, which was based primarily on observations the telescope made in December 2012, was an artifact or misinterpretation of some sort. "The best explanation still is plumes for that dataset, no doubt about it," he said

“Water is generally considered a basic prerequisite for life – at least as we know it on earth,” said Lorenz Roth, who was in charge of analysing the 2013 Hubble observations and who has been working at the Southwest Research Institute in America. “For this reason, the discovery of a water vapour plumes on the moon Europa has increasingly become a focus of extraterrestrial research.” The plumes eject material from the surface which will make further investigations of the moon Jupiter much easier in the future.

“We have been advancing the search for water and water plumes with multiple Hubble campaigns,” says Joachim Saur. “However, it was only after a camera on the Hubble Space Telescope in one of the last Space Shuttle Missions was repaired that we were able to achieve enough sensitivity to observe the fountains.”

The water plumes could only be seen in the observations when Europe was in a position in its orbit where the moon was furthest away from Jupiter. That means that the activity of the fountain varies temporally. Europa’s orbit is not quite circular but slightly elliptical. When Europa is furthest away from Jupiter in its orbit, the tidal forces cause the huge fractures in Europa’s ice surface to widen from which presumably the vapour is released.

Similar plumes of water vapour were discovered by the Cassini spacecraft on the Saturnian moon Enceladus. The activities there are similar to those on Europa during its orbit around its mother planet.

Comments

Probably just a result of our sporadic observations. One day, we will have constant eyes on every body in our system. This era of mystery will not last forever.

On a side note, I wonder what celestial impacts have on a deep ice surface with no atmosphere to slow it down other than the thick ice. The ice has to be constantly moving and rising to the surface over millions of years. If there is life there, then impacts would certainly eject the DNA of the native life into the cosmos.

Hopefully more data acquired under a wider range of conditions will help pin down the mystery of Europa's polar plumes. The existence of such plumes opens up the possibility of using aerogel collector technology like that employed in NASA's Stardust mission to collect samples of the plumes of Europa (and other targets like Io's volcanic plumes and even Jupiter's Gossamer rings) and return them to Earth for analysis at a fraction of the cost of today's flagship-class mission (never mind a much more expensive Europa lander mission).

Life needs a rich assortment of elements which so far this moon has not exhibited. Needless to say it's likely to have a rocky core, meaning there could be the rich assortment of metals and non metals needed for life but as to the actual construction of this moon, we've yet not a clue.

Some partially educated bumpkins think that since we have hydrocarbon eating worms on Earth, forgetting they evolved from an incredibly rich element assortment here, that hydrocarbon eating organisms can just magically evolve on a hydrocarbon/water moon with not a chance of life without those essential elements. At least a third of the periodic chart is needed for life...that's about 30 elements, to make DNA or RNA, hormones, enzymes to dissolve food into useful components etc.. Look up the elements say in a hormone or in DNA or RNA if you doubt this...or in proteins and lipids. A hydrocarbon life form is literally impossible for hydrogen and carbon do NOT form compounds past a small collection found in an oil well...devoid of life yet it's been around many millions of years and formed out of corpses of former life forms.